1. Field of the Invention.
The present invention relates to an asphalt distributor having extendable and retractable spray booms.
2. Description of the Prior Art.
In the prior art various asphalt spray booms, and other roadside spray units have been advanced. Folding booms have been used and longitudinally collapsible or telescoping booms have been used for spraying. The state of the prior art in asphalt spraying is represented by devices such as that shown in U.S. Pat. No. 4,315,602, which shows a roadside spray apparatus that permits lateral adjustment of separate booms relative to their supports, and provides for a typical spray control through the use of solenoid valves and the like.
A similar device is shown in U.S. Pat. No. 4,252,274. The spray booms in both of these patents can be pivoted as well as adjusted laterally.
An adjustable boom agricultural spray unit is shown in U.S. Pat. No. 3,514,038, using a sliding or telescoping boom that is operated through a linkage.
An extensible spraying apparatus shown in U.S. Pat. No. 2,965,307, and boom sections used on this apparatus are mounted relative to each other so that they will be extended or retracted on carriages or tracks. U.S. Pat. No. 2,518,952 shows a striping machine that is used for putting on traffic stripes, and which has concentric boom elements that telescope relative to each other to adjust the lateral spray width.
A mechanically operated telescoping boom assembly is shown in a plant spraying machine U.S. Pat. No. 1,024,239. The telescoping booms are operated by gears.
Telescoping support tubes for a plurality of spray heads is shown in U.S. Pat. No. 1,118,091.
Various breakaway joints have also been advanced for spray booms, such as that shown in U.S. Pat. No. 3,147,925.
Telescoping tube supports are also shown in U.S. Pat. No. 2,144,890 and other patents disclose adjustable booms, as well as extending and retracting members that vary the overall width of spraying or dust applying distributors. Such patents are exemplified by the following, which illustrate the general state of the art:
U.S. Pat. Nos. 395,176; 751,612; 869,958; 999,076; 198,014; 260,761; and 933,039.
When dealing with hot asphalt, substantial problems with extendable and retractable booms can be encountered when the asphalt is cooled and becomes thick and additionally the ability to accurately place the spray by insuring that the nozzles are turned on and off as the boom extends is an advantage that makes a difference for satisfactory operation.